(music) A bass guitar technique of hitting a string hard with the side of the thumb knuckle, producing a loud but brief snapping sound. Slapping is usually combined with popping, the act of pulling a string outward with the finger tip and letting it snap back. Invented by Larry Graham (Sly and the Family Stone, Graham Central Station).

Slap & pop bass sounds are very characteristic of disco and funk music, though around 1990 it got very popular again when bands like Red Hot Chilli Peppers, Primus, Infectious Grooves, and Faith No More hit the hard rock radio stations and Mtv.

Jazz players on upright bass (aka double bass) have a technique called "slapping", but it's a completely different technique that involves literally slapping the strings.

To have a very loud, good quality sound system esp. in your car. Or a song that just sounds hella good and has tremendous bass in it. I have to set the record str8 once again. We started this in the Town, Oakland, Ca, USA. When everybody else was still callin it "Knock" or "Thump" We in Oakland started calling it "Slap". The rest of the Bay Area eventually caught on to it. Str8 Up!